NO327382B1 - Antifouling coating agent, method of preparing the coating agent and using it as the outermost coating of a substrate used underwater - Google Patents

Description

This invention relates to antifouling coatings. An antifouling coating is used as a top coating on ship hulls and other surfaces such as fishing nets, oil rig legs, swimming pools and power station inlets to inhibit the deposition and growth of aquatic organisms such as shells and algae, generally by releasing a biocide for the aquatic the organisms.

The most successful antifouling paints in recent years have been "self-polishing copolymer" paints based on a polymeric binder to which biocidal triorganotin groups are chemically bound and from which the biocidal portions are gradually hydrolyzed by seawater, as described e.g. in GB-A-1 457 590. The polymer which the triorganotin groups are hydrolyses! from becomes soluble in seawater, so that when the outermost paint layer is depleted of biocide, it is washed away from the surface of the hull due to the ship's movement through seawater. There has been a demand for antifouling coatings that exhibit the "self-polishing" effect without necessarily releasing triorganotin constituents that are highly biocidal. Self-polishing copolymer paints that release non-biocide components are e.g. described in EP-A-69559 and WO-A-84/02915.

US-A-5 116 407 and EP-A-529 693 describe an antifouling coating with marine biocidal properties and which comprises as binder an acid-functional film-forming polymer whose acid groups are blocked by hydrolyzable blocking groups which are monoamine groups which form amine salts of the polymer which are soluble in organic solvents. JP-A-1-103 672 describes a similar mixture. WO-A-91/09915 describes an antifouling coating comprising a marine biocidal and a binder which is a hydrolysable seawater-erodible polymer containing sulfonic acid groups in quaternary ammonium salt form. IWO-A-96/03465 discloses an antifouling coating composition comprising a water-erodible binder polymer having at least 3 branches extending from a central core, with protected acid functionality present in the branches of the polymer. The protected acid functionality can be carboxylic or sulfonic acid groups blocked by a mono-amine or quaternary ammonium group.

JP-A-6-72807 discloses a resistant underwater antifouling agent containing a polymer having an average molecular weight of from 3,000 to 40,000, provided by the polymerization of (a) the reaction product of a polymerizable unsaturated monomer having a sulfonic acid group and at least one type of higher aliphatic amine represented by the general formula (I) where R<1> represents a saturated or unsaturated aliphatic hydrocarbon group of 12 to 20 carbon atoms, R2 represents a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R3 represents a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, a saturated or unsaturated aliphatic hydrocarbon group of 12 to 20 carbon atoms, or an alkyl group of 1 to 6 carbon atoms substituted by an amino group which may be substituted with an alkyl group of 1 to 6 carbon atoms, or, alternatively, by polymerization of the the above reaction product (a) and another polymerizable unsaturated monomer (b) which is copolymerizable r with this one.

EP-A-232 006 describes a water-erodible coating comprising an erodible polymer containing a hydrolysable sulfonate ester or sulfate ester group. EP-A-429 215 describes a process for producing such a polymer.

We have found that antifouling coating compositions based on a binder which is a salt of an amine having at least one aliphatic hydrocarbon group of 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid or acid phosphate ester can exhibit a "self- polishing" effect. However, the presence of sufficient of the highly hydrophilic sulfonate, sulfate, phosphonate, or phosphate groups to render the copolymer "self-polishing" may result in a weak water-swellable coating. We have found that this can be solved by using hydrophobic comonomers, but that the most hydrophobic comonomers, such as lauryl methacrylate or butyl acrylate, produce an undesirable soft copolymer with a very low Tg when used in conjunction with long-chain amine salts, and that coatings based on such a soft copolymer may have lower mechanical strength when wet than is desirable for use as an antifouling coating.

As described in US-A-5,116,407 and in JP-A-1-103,672, amines containing one aliphatic or cycloaliphatic hydrocarbon group of 12 to 20 carbon atoms are generally toxic to aquatic organisms. In some countries there is a demand for a "self-polishing" antifouling paint where the binder polymer is essentially non-toxic even if it is used with known biocides for aquatic organisms such as copper(l) oxide. We have found that, contrary to the disclosure in JP-A-6-72807, salts of a sulfonic acid copolymer with an amine having one methyl or ethyl group and two aliphatic hydrocarbon groups - each having 8 to 25 carbon atoms - are generally substantially non-toxic and can be used as the binder for a "self-polishing" antifouling paint. However, they are as water sensitive as other amine salts of sulfonic acid copolymers and are even softer than other amine salts. They can therefore be used in mixtures comprising a component with biocidal properties for aquatic organisms as the outermost coating on a substrate will be under water when used to inhibit the deposition and growth of aquatic organisms.

According to one aspect of the present invention, an antifouling coating composition comprises a binder which is a salt of an amine containing two aliphatic hydrocarbon groups of 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid or acid phosphate ester and at least one olefinically unsaturated comonomer characterized in that the copolymer contains at least 5 mol% units of an organocyclic ester or an organocyclic amide (A) of an olefinically unsaturated carboxylic acid, the coating mixture comprising a component with biocidal properties for aquatic organisms. By an organocyclic ester or amide we mean an ester of an alcohol, or an amide of an amine, and which contains at least one saturated, unsaturated or aromatic ring which can be carbocyclic or heterocyclic and substituted or unsubstituted and where the alcohol or amine group can be attached to the ring directly or through an alkylene or oxyalkylene bond.

The invention is described in the following with particular reference to sulfonic acid copolymers; in general, acid sulfate ester, phosphonic acid and acid phosphate ester copolymers can be used as alternatives to sulfonic acid copolymers.

We have found that the organocyclic ester or amide comonomer tends to make the copolymer both more hydrophobic and harder, compared to polymers prepared using only conventional hydrophobic acrylate ester comonomers such as butyl acrylate, 2-ethylhexyl acrylate or lauryl methacrylate. Copolymers containing organocyclic ester or amide monomer units and units of a sulfonic acid salt of an amine with at least one long-chain hydrocarbon group have improved resistance to cold flow and improved mechanical properties in service in seawater and are more resistant to damage while their " self-polishing" properties are maintained.

The organocyclic ester or amide (A) can e.g. be a cycloaliphatic, aryl, aralkyl or heterocyclic ester or amide. It is preferably a cycloaliphatic ester and is most preferably a bicyclic ester such as isobornyl methacrylate or -acrylate, bornyl acrylate or -methacrylate or norbomyl methacrylate or -acrylate or bicyclo(2,2,1)-5-heptene-2-methyl methacrylate or -acrylate, dicyclopentenyl or dicyclopentenyloxyethyl or dihydrocyclopentadienyl methacrylate or acrylate or a higher cyclic, e.g. tricyclic, ester such as adamantyl acrylate or -methacrylate. We have found that paints based on copolymers of such cycloaliphatic esters, most especially isobornyl esters, give the best mechanical properties in service in seawater. Alternatives are monocyclic esters such as cyclohexyl or cyclopentyl methacrylate or acrylate, menthyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, t-butylcyclohexyl acrylate or methacrylate or cyclohexylmethyl acrylate or methacrylate. The ester or amide (A) is preferably an ester of an alpha, beta-olefinic unsaturated carboxylic acid such as acrylic, methacrylic or itaconic acid. The amide is preferably a cycloaliphatic amide, most preferably a bicyclic (e.g. bornyl, iso-bornyl or norbornyl) amide or a higher cyclic, e.g. tricyclic, amide as described above for the esters. An example of a preferred cycloaliphatic amide is N-isobornyl acrylamide.

Thus, according to another aspect of the invention, an antifouling coating composition comprises a binder which is a salt of an amine containing at least one aliphatic hydrocarbon group with 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid or acid phosphate ester and at least one olefinically unsaturated comonomer, the coating mixture including a component with biocidal properties for aquatic organisms, characterized in that the copolymer contains at least 5 mol% units of an isobornyl ester or an amide of an olefinically unsaturated carboxylic acid.

Examples of aryl esters (A) are phenyl or naphthyl acrylate or methacrylate. Examples of aralkyl esters (A) are benzyl, naphthyloxyethyl, phenoxyethyl or phenylpropyl acrylate or methacrylate. Examples of heterocyclic esters (A) are furfuryl or tetrahydrofurfuryl methacrylate or acrylate.

The ester or amide monomer (A), especially a cycloaliphatic ester monomer such as isobornyl acrylate and/or isobornyl methacrylate, is present as at least 5 and preferably at least 10, most preferably at least 20, mol% of the copolymer, e.g. sulfonic acid copolymer, and may be present at up to 70 or 80 mol% or even more. More than one cycloaliphatic, aryl, aralkyl and/or heterocyclic ester monomer may be present if desired. The copolymer can e.g. be a binary copolymer of e.g. sulfonic acid amine salt and organocyclic ester monomer (A) or may additionally contain units of at least one ethylenically unsaturated comonomer. Examples of ethylenically unsaturated comonomers which can be copolymerized by addition polymerization with e.g. sulfonic acid or salt monomers and ester monomers (A) to form copolymers for use in the invention are acrylic acid or methacrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, isobutyl methacrylate, t-butyl acrylate, butyl methacrylate, isobutyl acrylate, 2-ethylhexyl methacrylate , lauryl methacrylate or stearyl methacrylate, styrene, vinyltoluene, acrylonitrile, acrylamide or N-alkylacrylamides such as N-t-octylacrylamide, vinyl acetate, vinyl butyrate, vinyl esters of higher carboxylic acids such as versatic acid (a mixture of branched 10-12C carboxylic acids) and vinyl chloride.

In order to achieve the desired hardness, toughness and Tg in combination with reduced water sensitivity, a copolymer comprising a sulfonic acid amine salt as defined, at least 5, most preferably at least 10, mol% of an organocyclic ester (A) as defined and at least 5, most preferably at least 10, mol% of an acyclic alkyl ester (B) of an olefinically unsaturated carboxylic acid with 4 to 20, most preferably 4 to 8, carbon atoms in the alkyl group being preferred. The acyclic alkyl ester can e.g. be butyl acrylate or isobutyl methacrylate. The total amount of units (A) and (B) in the copolymer is preferably at least 40 mol%, more preferably at least 60 mol%, up to 70 or 80 mol% or even more. Most preferably, the copolymer is a terpolymer consisting mainly of sulphonic acid amine salt units and units of monomers (A) and (B).

According to a third aspect of the invention, there is thus provided an antifouling coating composition comprising a binder which is a salt of an amine containing at least one aliphatic hydrocarbon group of 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulphonic acid, acid sulphate ester, phosphonic acid or acid phosphate ester and at least one olefinically unsaturated comonomer, the coating mixture including a component with biocidal properties for aquatic organisms, characterized in that the copolymer contains at least 5 mol% of an organocyclic ester (A) of an olefinically unsaturated carboxylic acid, preferably of one of the types mentioned above , and at least 5 mol% of an acyclic alkyl ester (B) of an olefinically unsaturated carboxylic acid with 4 to 20 carbon atoms in the alkyl group, the total amount of units (A) and (B) in the copolymer being at least 40 mol%.

An alternative preferred copolymer contains at least 5 mol% of units of an organocyclic acrylate ester and at least 5 mol% of units of an organocyclic methacrylate ester. The organocyclic acrylate and methacrylate esters are preferably cycloaliphatic esters, e.g. isobornyl acrylate and -methacrylate. More preferably, the copolymer contains at least 15 or 25 mol% each, up to a total amount of 70 or 80 mol%, of the units of organocyclic acrylate and methacrylate esters, e.g. a terpolymer of sulfonic acid amine salt units and isobornyl acrylate and methacrylate units.

According to a fourth aspect of the invention, there is thus provided an antifouling coating composition comprising a binder which is a salt of an amine containing at least one aliphatic hydrocarbon group with 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulphonic acid, acid sulphate ester, phosphonic acid or acid phosphate ester and at least one olefinically unsaturated comonomer, the coating mixture comprising a component with biocidal properties for aquatic organisms, characterized in that the copolymer contains at least 5 mol% of an organocyclic acrylate ester and at least 5 mol% of an organocyclic methacrylate ester. The organocyclic esters are preferably of the types mentioned above.

The olefinically unsaturated acid monomer for the addition copolymer with which the amine forms a salt is preferably a sulfonic acid. Examples of sulfonic acid monomers that can be used to produce the copolymer are acrylic monomers such as 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 2-sulfoethyl acrylate (CH2=CHCOOCH2CH2S03H) or 2-sulfoethyl methacrylate, styrenesulfonic acid (e.g. p-styrenesulfonic acid), vinyl sulfonic acid or methallyl sulfonic acid. An example of an acidic sulfate ester monomer is the sulfuric acid monoester of hydroxyethyl methacrylate (meth-acryloxyethyl monosulfate). Examples of phosphonic acid monomers are vinylphosphonic acid, styrenephosphonic acid and 2-acrylamido-propanephosphonic acid. Phosphonic acids are usually dibasic and preferably have both acid groups in amine salt form or can have one acid group esterified. Examples of acidic phosphate ester monomers are methacryloxyethyl monophosphate and acryloxyethyl monophosphate. The copolymer generally contains at least 5 mol%, preferably at least 10 mol%, of the monomer units with sulfonic acid etc. functionality, up to 50 mol%, preferably up to 40 mol%. Most preferably, the copolymer contains at least 15 mol%, up to 30 to 35 mol% sulfonic acid etc. monomer units.

The amine is preferably a tertiary amine, although secondary amines and, in some aspects, primary amines may alternatively be used. We have found that a binder which is a tertiary amine salt of a sulfonic acid functional polymer gives a lower and more stable paint viscosity if a solution of the binder is mixed with a biocide pigment which is a copper or zinc compound that is poorly soluble in seawater, compared to primary or secondary amine salts. In many cases, a substantially non-toxic amine is preferred, with two aliphatic hydrocarbon groups, each having 8-25, e.g. 8-20, preferably 12-18, carbon atoms as described above. Tertiary amines containing one methyl or ethyl group in addition to the C8-20 aliphatic groups are particularly preferred, e.g. methylbis-(hydrogenated tallow)amine (M2HT), methyldioctadecylamine, methyldioctylamine or methyldicocosamine. M2HT has the chemical formula CH3NR2, where R represents a mixture of alkyl radicals, mainly octadecyl and hexadecyl, derived from hydrogenated tallow. Similarly, methyldicocosamine contains a mixture of alkyl radicals, mainly dodecyl and tetradecyl, derived from coconut oil.

Examples of alternative amines for use in some aspects of the invention are dimethyldodecylamine, dimethylhexadecylamine, dimethyloleylamine, dimethylabiethylamine, dimethylhydrogenated tallow amine, or dimethylcocosamine. Tertiary amines containing one long-chain aliphatic radical with 8-25 carbon atoms together with two lower alkyl groups, e.g. with up to 4 carbon atoms such as methyl, e.g. dimethyldodecylamine, dimethyloleylamine, dimethylabiethylamine or dimethylcocosamine, usually have biocidal properties against certain aquatic organisms such as algae and shells, and may be preferred for use as the sole ingredient with aquatic biocidal properties or to enhance other biocides present in the antifouling coating. Examples of primary amines are dodecylamine, hexadecylamine, octadecylamine, oleylamine, dehydro-abiethylamine (Rosin Amine D) and hydrogenated tallow amine. Examples of secondary amines are N-methyldodecylamine and N-methylcocosamine.

The copolymers according to the invention can be produced using different methods, which will be discussed in the following in relation to sulphonic acids, although similar methods can be used for the acid sulphate esters, the phosphoric acids and the acid phosphate esters. In one process, a polymerizable olefinically unsaturated sulfonic acid is reacted with is amine and the resulting amine salt of the unsaturated sulfonic acid is copolymerized with the monomer (A) and optionally with one or more olefinically unsaturated comonomers to form a copolymer which is an amine salt of a sulfonic acid functional polymer . Alternatively, a sulfonic acid functional copolymer containing units (A) is reacted with an amine to form an amine salt of the sulfonic acid functional polymer.

If the polymerizable olefinically unsaturated sulphonic acid is reacted with an amine to form a salt before polymerisation, this reaction is preferably carried out in an organic solvent, e.g. an alcohol such as n-butanol, an ether alcohol such as butoxyethanol or methoxypropanol, an ester such as butyl acetate or isoamyl acetate, an ether ester such as ethoxyethyl acetate or methoxypropyl acetate, a ketone such as methyl isobutyl ketone or methyl isoamyl ketone, or an aromatic hydrocarbon such as xylene, toluene or trimethylbenzene, or a mixture of two or more of these solvents. The solvent can be miscible with water or immiscible with water. Certain sulfonic acid monomers, such as AMPS, are insoluble in most common organic solvents, but their salts with amines having at least one C8-25 hydrocarbon group are usually soluble in the solvents listed above. Thus, the amine and sulfonic acid can be mixed in the organic solvent to produce a solution of the amine salt of the sulfonic acid; for an insoluble sulfonic acid, visual disappearance of the sulfonic acid indicates completion of the salt-forming reaction. Many long-chain amines are solids, such as M2HT, which melts at approx. 35°C. A solid amine is preferably either melted before mixing with the sulfonic acid or heated to melt it as it is mixed with the sulfonic acid. The salt-forming reaction is generally exothermic. The amine sulfonic acid salt can, if desired, be isolated, e.g. by evaporation of solvent or in some cases by slow crystallization of the salt at or below ambient temperature, but it is preferably used in solution.

The amine salt of the olefinically unsaturated sulfonic acid can be polymerized by addition polymerization with the required comonomer(s). Polymerization is preferably carried out in an organic solvent, e.g. a solvent as indicated above or a mixture of two or more of these solvents, using a free radical initiator such as an azo compound, e.g. azobis-isobutyronitrile or azobis-(methylbutyronitrile), or a peroxide such as benzoyl peroxide. Most preferably, the polymerization is carried out in a solvent which at least partially comprises the solvent in which the amine salt is prepared, so that the solution of amine salt as prepared can be added directly to the polymerization reaction. The polymerization temperature is generally in the range 50-150°C, preferably 60-120°C. Polymerization can be carried out with all the monomers present at the start of the reaction, or one or more of the monomers can be added as the polymerization progresses. A chain transfer agent, e.g. a mercaptan such as dode-can-1-thiol can be used, if necessary, to regulate the molecular weight of the copolymer formed.

The weight average molecular weight of the copolymer (Mw) as determined by gel permeation chromatography is generally at least 1,000, preferably at least 2,000, to provide the required film strength of the coating after application, while generally being below 150,000, preferably below 100,000 and most preferably no more than 60,000, to achieve a paint viscosity low enough for spraying at a high solids level.

Alternatively, the olefinically unsaturated sulfonic acid can be polymerized using similar polymerization conditions as those stated above, and preferably using a solvent in which the sulfonic acid and comonomer(s) are soluble, and the formed sulfonic acid polymer can be reacted with the amine. For some sulfonic acid monomers, especially AMPS, it can be difficult to find a suitable polymerization solvent and in that case polymerization of the amine salt is preferred.

If there is a need for water-based paint, the amine salt of the sulfonate-functional polymer can be prepared in organic solvent solution and dispersed in water, usually with the help of a surface-active agent. The organic solvent can be partially or substantially completely removed from the resulting dispersion. E.g. the sulfonate salt binder polymer can be prepared in a solvent more volatile than water or form an azeotrope with water and the solvent can be removed by distillation.

In an alternative preparation method for an aqueous dispersion of an amine salt of a sulfonate-functional binder polymer, the polymer can be prepared by emulsion or suspension polymerization. An amine salt of an ethylenically unsaturated sulphonic acid can e.g. is copolymerized with at least one ethylenically unsaturated comonomer as an oil-in-water emulsion using an anionic, cationic, nonionic or amphoteric surfactant in the presence of a free radical initiator.

The solution, dispersion or emulsion of the binder polymer can be used as a clear antifouling varnish if the amine used has adequate biocidal properties for aquatic organisms, but it is more common that it is mixed with a biocide (a component with biocidal properties) for aquatic organisms and usually with a pigment, using conventional paint mixing techniques. The biocide itself can be all or part of the pigment in the paint. If it is pigmented, the coating mixture preferably has a pigment volume concentration of e.g. 15 to 55%. The pigment preferably comprises at least one poorly soluble metal-containing pigment with a solubility in seawater of from 0.5 to 100, preferably 1 to 10, parts by weight. million. Examples of such pigments which are also aquatic biocides include copper or zinc compounds, such as copper (l) oxide, copper (l) thiocyanate, copper (l) sulfate, zinc ethylene bis(dithiocarbamate), zinc dimethyldithiocarbamate, zinc pyrithione , copper pyrithione, zinc diethyldithiocarbamate, copper resinate or copper(l)-ethylenebis-(dithiocarbamate) and certain other slightly seawater-soluble metal-containing pigments, e.g. manganese ethylene bis-(dithiocarbamate). Other poorly soluble pigments, with a solubility in seawater of 0.5 to 100, preferably 0.5 or 1 to 10, parts per million, includes barium sulphate, calcium sulphate, dolomite and zinc oxide. Copper metal may be present as an aquatic biocide, e.g. in flake or powder form.

The poorly soluble metal-containing pigments produce water-soluble metal compounds by reaction with seawater, so that the pigment particles do not survive on the paint surface. This promotes the "self-polishing" effect of the paint where the amine group is gradually released from the surface of the paint film through interaction with seawater components to give a polymer containing free sulfonic acid groups, which gradually dissolves in seawater. Mixtures of poorly soluble pigments can be used, and e.g. Copper (l) oxide, copper (l) thiocyanate or zinc ethylene bis(dithiocarbamate), which are very effective biocidal pigments, can be mixed with zinc oxide, which is not effective as a biocide, but which dissolves a little faster in sea water.

The antifouling coating composition may contain a non-metallic biocide for marine organisms, e.g. tetramethylthiuram disulfide, methylenebis(thiocyanate), captan, pyridinetriphenylboron, a substituted iso-thiazolone such as 4,5-dichloro-2-N-octyl-4-isothiazolin-3-one, 2-methylthio-4-t-butylamino- 6-cyclopropylamino-s-triazine, N-3,4-dichlorophenyl-N',N'-dimethyl-urea ("Diuron"), 2-(thiocyanomethylthio)-benzothiazole, 2,4,5,6-tetra -chloroisophthalonitrile, dichlorofluanid, tolylfluanid or 2,3,5,6-tetrachloro-4-(methylsulfonyl)-pyridine. Such a non-metal-containing biocide can be used in addition to a poorly soluble copper or zinc compound, or one or more non-metal-containing biocides can be used as the only biocide in the coating in a copper-free, or even metal-free or pigment-free, antifouling coating. Many of these non-metallic biocides are solid and all are poorly soluble in seawater and can promote the "self-polishing" effect of the paint. The component with biocidal properties may be present at 0.01 to 90% by weight of the composition, depending on its biocidal effectiveness.

The coating mixture may additionally contain a pigment which is not reactive with seawater and which may be very insoluble in seawater (solubility below 0.5 parts per million by weight) such as titanium dioxide or iron(lll)-oxide or an organic pigment such as phthalocyanine or azo pigment. Such highly insoluble pigments are preferably used with less than 60% by weight of the total pigment component in the paint, most preferably less than 40%.

The coating mixture may also contain one or more plasticizers, e.g. a chlorinated paraffin, a phthalate diester or a phosphate triester, and/or one or more auxiliary film-forming agents, e.g. a vinyl polymer, such as a copolymer of vinyl chloride with a vinyl ether, a vinyl ester such as vinyl acetate, vinyl alcohol and/or an acrylic monomer or a hydrocarbon resin. Softeners and/or auxiliary film-forming agents, if such are present, are generally used at up to 30% by volume, based on the dry paint film, preferably 5-20% by volume. The coating mixture may additionally contain conventional thickeners, especially thixotropics such as silica or bentonite, and/or stabilizers such as zeolites.

The invention is illustrated by the following examples.

Example 1

a) Preparation of binder polymer

Acrylamido-2-methylpropanesulfonic acid (AMPS, 62.9 g) was neutralized with

methyl bis(hydrogenated tallow)amine (M2HT, 159.1 g) in xylene (90 g) and butanol (30 g) to give a solution of the M2HT salt of AMPS. Isobornyl acrylate (173.9 g), butyl acrylate (48.6 g) and azobismethylbutyronitrile (2.9 g) were added and the combined solution polymerized by slow addition to a stirred reaction vessel containing xylene (123.8 g) and butanol ( 41.2 g) at 90°C. Thirty minutes after the monomer addition was complete, a suspension of azobisisobutyronitrile (AiBN, 1.2 g) in xylene (5.6 g) and butanol (1.9 g) was added to the reaction vessel, and after another 45 minutes a second suspension of AiBN (1.2 g) in xylene (5.6 g) and butanol (1.9 g) was added to the reaction vessel, the vessel being held at 90°C during this time and for a further 60 minutes.

The product was a 60% by weight solution in xylene and butanol (3:1 by weight) of a copolymer of the M2HT salt of AMPS (20 mpl%), isobornyl acrylate (55 mol%) and butyl acrylate (25 mol%). The copolymer had a weight average molecular weight of approx. 6,500.

b) Paint production

27.8% (all percentages are weight percentages) of the above copolymer solution was mixed with 15.9% solvent (xylene, butanol and methyl isoamyl ketone), 0.1% hydroquinone stabilizer, 2.0% thickeners (bentonite clay and silica airgel) , 6.4% plasticizers ("Lutonal" vinyl chloride copolymer and chlorinated paraffin) and 47.8% pigments (copper(l) oxide, zinc ethylene bis-(dithiocarbamate), zinc oxide,

titanium dioxide and C.l. pigment red) in a high-speed dispersing device to form a self-polishing antifouling paint.

As a test of antifouling performance, the paint was applied to a veneer sheet that had first been painted with a commercial anti-corrosion primer (JVA202/203, International Paints) and the sheet was immersed in the sea at Newton Ferrers, Devon, England; a place that is particularly prone to algae growth. Certain paints were also tested in a similar way in the sea at Burnham-on-Crouch, Essex, England; a place that is particularly prone to shell growing. The paint film was periodically assessed for the deposition of marine growth organisms, and results are shown in Table 2 below.

As a test of self-polishing performance, the paint was also tested on a rotating disc apparatus of the type described in GB-A-1 457 590, and the film thickness measured before and after rotation in seawater. The mechanical properties of the paint film were also assessed during this period. Results are shown in table 2 below.

Examples 2-17 and comparative examples C1 and C4

By following the procedures of Example 1a, copolymers with the mole percent compositions shown in Table 1 below were prepared in solution at the weight percent and in the solvent indicated.

Self-polishing antifouling paints were prepared following the procedure and composition of Example 1 b, but using the copolymer solutions prepared in Examples 2-17 or C1 or C4 instead of the copolymer solution of Example 1. The paints were evaluated for antifouling and self-polishing performance and for mechanical properties as described in example 1. The results are shown in table 2 below.

Comparative example C2

A commercial organotin-based SPC paint (BFA976, International Paint) was tested for antifouling, self-polishing and mechanical performance as described above. Results are shown in table 2 below.

Comparative example C3

A commercial anticorrosive primer (JVA202/203, International Paints) was tested for antifouling, self-polishing and mechanical performance as described above. Results are shown in table 2 below.

Claims (17)

1. Antifouling coating composition, comprising a binder which is a salt of an amine containing two aliphatic hydrocarbon groups with 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid or acid phosphate ester and at least one olefinically unsaturated comonomer, characterized by the copolymer contains at least 5 mol% units of an organocyclic ester or an organocyclic amide (A) of an olefinically unsaturated carboxylic acid, the coating mixture comprising a component with biocidal properties for aquatic organisms. 2. Anti-growth coating mixture according to claim 1, characterized in that the amine is a tertiary amine with one methyl or ethyl group in addition to two aliphatic hydrocarbon groups, each with 8 to 20 carbon atoms. 3. Anti-growth coating mixture according to claim 2, characterized in that the amine is methylbis-(hydrogenated tallow)-amine. 4. Antifouling coating composition, comprising a binder which is a salt of an amine containing at least one aliphatic hydrocarbon group with 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid or acid phosphate ester and at least one olefinically unsaturated comonomer, wherein the coating mixture comprises a component with biocidal properties for aquatic organisms, characterized in that the copolymer contains at least 5 mol% units of an organocyclic ester (A) of an olefinically unsaturated carboxylic acid and at least 5 mol% units of an acyclic alkyl ester (B) of an olefinically unsaturated carboxylic acid with 4 to 20 carbon atoms in the alkyl group, the the total amount of units (A) and (B) in the copolymer is at least 40 mol%. 5. Antifouling coating mixture according to any one of claims 1 to 4, characterized in that the ester (A) is a cycloaliphatic ester. 6. Anti-growth coating mixture according to claim 5, characterized in that the cycloaliphatic ester is isobornyl acrylate or -methacrylate. 7. Antifouling coating composition, comprising a binder which is a salt of an amine containing at least one aliphatic hydrocarbon group of 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid, acid phosphate ester, and at least one olefinically unsaturated comonomer, as the coating mixture comprises a component with biocidal properties for aquatic organisms, characterized in that the copolymer contains at least 5 mol% units of an organocyclic acrylate ester and at least 5 mol% units of an organocyclic methacrylate ester. 8. Anti-growth coating mixture according to claim 7, characterized in that the organocyclic acrylate and methacrylate esters are cycloaliphatic esters. 9. Anti-growth coating mixture according to claim 8, characterized in that the cycloaliphatic esters are isobornyl acrylate and isobornyl methacrylate. 10. Antifouling coating composition, comprising a binder which is a salt of an amine containing at least one aliphatic hydrocarbon group with 8 to 25 carbon atoms and an addition copolymer of an olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid or acid phosphate ester and at least one olefinically unsaturated comonomer, wherein the coating mixture comprises a component with biocidal properties for aquatic organisms, characterized in that the copolymer contains at least 5 mol% units of an isobornyl ester or an isobornylamide of an olefinically unsaturated carboxylic acid. 11. Anti-fouling coating mixture according to any one of claims 6, 9 and 10, characterized in that the copolymer contains 20 to 80 mol% of isobornyl acrylate and/or methacrylate units. 12. Antifouling coating mixture according to any one of claims 4 to 11, characterized in that the amine is a tertiary amine containing one aliphatic radical with 8 to 25 carbon atoms together with two lower alkyl groups. 13. Anti-fouling coating mixture according to any one of claims 1 to 12, characterized in that the copolymer contains 15 to 40 mol% of olefinically unsaturated sulfonic acid units. 14. Anti-growth coating mixture according to claim 13, characterized in that the olefinically unsaturated sulphonic acid is 2-acrylamido-2-methylpropane sulphonic acid. 15. Antifouling coating mixture according to any one of claims 1 to 14, characterized in that the mixture contains at least one plasticizer or one aid for film formation, and which is present at 5 to 30% by volume of the dry paint. 16. Method for producing an antifouling coating mixture according to any one of claims 1 to 14, characterized in that the said amine and the olefinically unsaturated sulfonic acid, acid sulfate ester, phosphonic acid or acid phosphate ester are reacted to produce an amine salt in an organic solvent which is a solvent for the produced amine salt, the resulting amine salt solution being polymerized with at least one olefinically unsaturated comonomers comprising an organocyclic ester or an organocyclic amide present with at least 5 mol% of total monomers, in the presence of a free radical initiator to produce a binder solution, and the binder solution is mixed with a component having biocidal properties for aquatic organisms. 17. Use of a mixture according to any one of claims 1 to 15 as the outermost coating of a substrate to be used under water, to prevent the deposition and growth of aquatic organisms.